The present invention relates to a method and apparatus for separating oil from oil-absorbent materials so that both the materials and the oil can be recycled.
The desorption of oil and other industrial lubricants from absorbent materials such as pads or xe2x80x9csocksxe2x80x9d is a prevalent industrial process. As a result, the current art contains a variety of different methods by which oil is either removed from an oil absorber or process after recovery for recycle of the oil or the materials are cleaned for reuse.
The steps that are used to separate and recover oil from oil-absorbing materials for recycle must be chosen so that the desired results: maximum recycling and minimum waste generation are achieved. This type of optimization inevitably results in a process that is specific to a particular waste stream; that is, it will be dictated by the oil absorber and the composition of absorbed fluids and entrained solids.
The steps that are used to clean the oil-absorbing materials are dictated by those processes that will result in the cleanest materials. However, the goals of maximum recycle of absorbed oil and cleanest materials are not obtained necessarily by the same processes.
Therefore, there remains a need for an oil recovery process that is simple, effective and that allows the recovery of the oil as well as the recycling of clean oil-absorbing material.
According to its major aspects and briefly stated, the present invention is a method and system for recovering oil and other lubricants from absorbent materials so that both the materials and the recovered oil can be recycled. In the case of the materials, recycle means that the materials are clean and ready for reuse following application of the present process. In the case of oil that is removed from these materials, recycle means that the oil may require refining but it is substantially free of water, dirt, and metal shavings, chips and particles.
The system comprises two major components: an excess oil removal component and a dry cleaning component. In the first component, excess oil is removed from the materials and then treated to separate clean oil from contaminated, dirty oil. In the second component, the cleaning component, there is a closed loop dry cleaning machine connected to a pair of industrial distillers, a dry cleaning fluid tank for storing the distilled dry cleaning fluid, and a waste container.
In the first component, substantial excess oil is drained by gravity into a sump. However, additional excess oil is removed by centrifuging. The excess oil that is removed is pumped to a settling tank where, after a period of time, the clean oil at the top is forwarded to a used oil container and the water-contaminated oil is sent to an evaporator. After evaporating the water from this water-contaminated oil, it, too, is forwarded to the used oil container.
In the cleaning component, the effluent from drycleaning the materials is distilled twice to remove as much oil from the dry cleaning fluid as possible and to assure that the drycleaning fluid, when reused to dry clean the materials, is as clean as possible. The oil removed from the distillers is contaminated and is handled accordingly.
An important feature of the present invention is the use of centrifuging in combination with dry cleaning. Centrifuging removes sufficient oil so that the absorbent materials could simply be reused as absorbers if desired, but could be cleaned if desired by simply washing them. Dry cleaning also, by itself, would clean the pads without the need for centrifuging although draining or wringing out materials saturated with oil prior to dry cleaning makes a good deal of sense. Importantly, centrifuging is not need to clean the materials and dry cleaning is not needed to recycle the oil in the materials. However, when the goal of the process is both to recycle absorbed oil and recycle clean oil-absorbing materials, as well as minimize the waste from the dry cleaning machine and limit damage from metal particles and chips, the combination of centrifuging and dry cleaning achieves these dual, conflicting goals.
A feature of the present invention is the first component. A considerable amount of oil can be removed from oil-absorbent materials simply by allowing them to drain; however, even less oil will remain in these materials after centrifuging. By minimizing the amount of residual oil in the materials in the first component of the present process, more oil is recovered and the dry cleaning component is more effective in cleaning the materials for recycle. Furthermore, metal chips and particles can be removed by centrifusing before drycleaning the materials
Another important feature of the present invention is the use of two industrial distillers to separate dry cleaning fluid, preferably perchloroethyene, from the residual oil that has been removed from the oil absorbing materials through dry cleaning. The purpose of double distillation is to assure that the perchloroethylene that is repeatedly used for dry cleaning the materials is clean when it enters the dry cleaning machine for reuse.
Still another feature of the present invention is the use of gravity draining to remove excess oil before centrifuging. Not only does excess oil drain readily from the absorbing materials, but also particles and metal chips can be removed in this way. This step makes centrifuging and dry cleaning more efficient.
Yet another feature of the present invention is the use of an evaporator to remove water from the recovered oil. Oil/water separation by specific gravity prior to this step is a cost-effective way to obtain significant separation but oil recovery can be significantly improved by evaporation.
The use of an industrial distiller rather than a typical dry cleaning machine distiller is another important feature of the present invention. Because both the internal temperature and pressure can be precisely controlled, the independent distiller allows a more effective separation of the perchloroethylene from the lubricants. This in turn maximizes the purity of the recycled perchloroethylene and increases the recovery of lubricants.
Other features and advantages of the present invention will be apparent to those skilled in the art from a careful reading of the Detailed Description of a Preferred Embodiment presented below.